MountService初探

MountService作为Vold的客户端，会接收来自vold的消息，并且内部定义保存了各种Volume相关的状态定义： 1、VolumeState

class VolumeState {
        public static final int Init       = -1;
        public static final int NoMedia    = 0;
        public static final int Idle       = 1;
        public static final int Pending    = 2;
        public static final int Checking   = 3;
        public static final int Mounted    = 4;
        public static final int Unmounting = 5;
        public static final int Formatting = 6;
        public static final int Shared     = 7;
        public static final int SharedMnt  = 8;
    }

VoldResponseCode

class VoldResponseCode {
        /*
         * 100 series - Requestion action was initiated; expect another reply
         *              before proceeding with a new command.
         */
        public static final int VolumeListResult               = 110;
        public static final int AsecListResult                 = 111;
        public static final int StorageUsersListResult         = 112;
        public static final int CryptfsGetfieldResult          = 113;

        /*
         * 200 series - Requestion action has been successfully completed.
         */
        public static final int ShareStatusResult              = 210;
        public static final int AsecPathResult                 = 211;
        public static final int ShareEnabledResult             = 212;

        /*
         * 400 series - Command was accepted, but the requested action
         *              did not take place.
         */
        public static final int OpFailedNoMedia                = 401;
        public static final int OpFailedMediaBlank             = 402;
        public static final int OpFailedMediaCorrupt           = 403;
        public static final int OpFailedVolNotMounted          = 404;
        public static final int OpFailedStorageBusy            = 405;
        public static final int OpFailedStorageNotFound        = 406;

        /*
         * 600 series - Unsolicited broadcasts.
         */
        public static final int VolumeStateChange              = 605;
        public static final int VolumeUuidChange               = 613;
        public static final int VolumeUserLabelChange          = 614;
        public static final int VolumeDiskInserted             = 630;
        public static final int VolumeDiskRemoved              = 631;
        public static final int VolumeBadRemoval               = 632;

        /*
         * 700 series - fstrim
         */
        public static final int FstrimCompleted                = 700;
    }

1、MountService构造方法： 1.1、初始化MountService静态对象sSelf以及PackageManagerService，readStoregeListLocked方法会读取系统配置文件，初始化mVolumes对象。

sSelf = this;

        mContext = context;

        synchronized (mVolumesLock) {
            readStorageListLocked();
        }

        // XXX: This will go away soon in favor of IMountServiceObserver
        mPms = (PackageManagerService) ServiceManager.getService("package");

readStorageListLocked方法，读取storage_list.xml文件。

private void readStorageListLocked() {
        mVolumes.clear();
        mVolumeStates.clear();

        Resources resources = mContext.getResources();

        int id = com.android.internal.R.xml.storage_list;
        XmlResourceParser parser = resources.getXml(id);
        AttributeSet attrs = Xml.asAttributeSet(parser);

我这边的手机读取结果为：

04-21 21:50:36.230 D/MountService( 1269): got storage path: /storage/sdcard0 description: 内部存储设备 primary: true removable: false emulated: true mtpReserve: 100 allowMassStorage: false maxFileSize: 0 allowMtp: true

如果是模拟分区，则：

 if (emulated) {
                        // For devices with emulated storage, we create separate
                        // volumes for each known user.
                        mEmulatedTemplate = new StorageVolume(null, descriptionId, true, false,
                                true, mtpReserve, false, maxFileSize, null, allowMtp);

                        final UserManagerService userManager = UserManagerService.getInstance();
                        for (UserInfo user : userManager.getUsers(false)) {
                            createEmulatedVolumeForUserLocked(user.getUserHandle());
                        }

                    } 

即：初始化mEmulatedTemplate。 如果不为 ：则构建StorageVolume，并加入到mVolumes中。

else {
                        if (path == null || description == null) {
                            Slog.e(TAG, "Missing storage path or description in readStorageList");
                        } else {
                            final StorageVolume volume = new StorageVolume(new File(path),
                                    descriptionId, primary, removable, emulated, mtpReserve,
                                    allowMassStorage, maxFileSize, null, allowMtp);
                            addVolumeLocked(volume);

                            // Until we hear otherwise, treat as unmounted
                            mVolumeStates.put(volume.getPath(), Environment.MEDIA_UNMOUNTED);
                            volume.setState(Environment.MEDIA_UNMOUNTED);
                        }

1.2、开辟MountServcieHandler子线程

HandlerThread hthread = new HandlerThread(TAG);
        hthread.start();
        mHandler = new MountServiceHandler(hthread.getLooper());

1.3、注册用户相关广播，多用户相关。

final IntentFilter userFilter = new IntentFilter();
        userFilter.addAction(Intent.ACTION_USER_ADDED);
        userFilter.addAction(Intent.ACTION_USER_REMOVED);
        mContext.registerReceiver(mUserReceiver, userFilter, null, mHandler);

1.4、如果主Volume设备允许massStorage，则监听usb状态：

// Watch for USB changes on primary volume
        final StorageVolume primary = getPrimaryPhysicalVolume();
        if ((primary != null && primary.allowMassStorage()) ||
            //ignore primary config, force to register if property is true
            SystemProperties.getBoolean("persist.sys.ums", true)) {
            mContext.registerReceiver(
                    mUsbReceiver, new IntentFilter(UsbManager.ACTION_USB_STATE), null, mHandler);
        }

1.5、构建NativeDaemonConnector，用户和vold进行socket通信。并为其开辟单独线程：

mConnector = new NativeDaemonConnector(this, "vold", MAX_CONTAINERS * 2, VOLD_TAG, 25,
                null);

        Thread thread = new Thread(mConnector, VOLD_TAG);
        thread.start();

NativeDaemonConnector将会和vold进程的CommandListener进行通信，第二个参数为vold，标示和vold进行通信，第一个参数为INativeDaemonConnectorCallbacks，其有三个回调：

void onDaemonConnected();
    boolean onCheckHoldWakeLock(int code);
    boolean onEvent(int code, String raw, String[] cooked);

在和vold通信过程中，会回调执行onEvent方法。

2、在系统启动时，还会执行器systemReady方法：

public void systemReady() {
        mSystemReady = true;
        mHandler.obtainMessage(H_SYSTEM_READY).sendToTarget();
    }

case H_SYSTEM_READY: {
                    try {
                        handleSystemReady();
                    } catch (Exception ex) {
                        Slog.e(TAG, "Boot-time mount exception", ex);
                    }
                    break;
                }

在handleSystemReady中，会遍历当前存储块区，并更新其状态：

// Push mounted state for all emulated storage
        synchronized (mVolumesLock) {
            for (StorageVolume volume : mVolumes) {
                if (volume.isEmulated()) {
                    updatePublicVolumeState(volume, Environment.MEDIA_MOUNTED);
                }
            }
        }

3、和vold进程通信，MountService会执行其onEvent方法：

public boolean onEvent(int code, String raw, String[] cooked) {
    if (code == VoldResponseCode.VolumeStateChange) {
    } else if (code == VoldResponseCode.VolumeUuidChange) {
    } else if (code == VoldResponseCode.VolumeUserLabelChange) {
    } else if ((code == VoldResponseCode.VolumeDiskInserted) ||
                   (code == VoldResponseCode.VolumeDiskRemoved) ||
                   (code == VoldResponseCode.VolumeBadRemoval)) {
    } else if (code == VoldResponseCode.VolumeDiskRemoved) {
    } else if (code == VoldResponseCode.VolumeBadRemoval) {
    } else if (code == VoldResponseCode.FstrimCompleted) {
    }
    。。。。
}

4、附storate_list.xml文件内容：

<StorageList xmlns:android="http://schemas.android.com/apk/res/android">
    <!-- internal emulated storage -->
    <storage android:mountPoint="/storage/sdcard0"
            android:storageDescription="@string/storage_internal"
            android:primary="true"
            android:emulated="true"
            android:removable="false"
            android:mtpReserve="100" />
        <storage android:mountPoint="/storage/sdcard1"
            android:storageDescription="@string/storage_sd_card"
            android:primary="false"
            android:emulated="false"
            android:removable="true"
            android:allowMassStorage="true" />
        <storage android:mountPoint="/storage/uicc0"
            android:storageDescription="@string/storage_uicc"
            android:primary="false"
            android:emulated="false"
            android:removable="true"
            android:allowMassStorage="true" />
        <storage android:mountPoint="/storage/uicc1"
            android:storageDescription="@string/storage_uicc"
            android:primary="false"
            android:emulated="false"
            android:removable="true"
            android:allowMassStorage="false"
            android:allowMtp="false" />
        <storage android:mountPoint="/storage/usbotg"
            android:storageDescription="@string/storage_usb"
            android:primary="false"
            android:emulated="false"
            android:removable="true"
            android:allowMassStorage="false" />
</StorageList>

log描述：

04-21 21:50:36.230 D/MountService( 1269): got storage path: /storage/sdcard0 description: 内部存储设备 primary: true removable: false emulated: true mtpReserve: 100 allowMassStorage: false maxFileSize: 0 allowMtp: true

04-21 21:50:36.232 D/MountService( 1269): addVolumeLocked() StorageVolume:

04-21 21:50:36.232 D/MountService( 1269):     mStorageId=65537 mPath=/storage/emulated/0 mDescriptionId=17040809 

04-21 21:50:36.232 D/MountService( 1269):     mPrimary=true mRemovable=false mEmulated=true mMtpReserveSpace=100 

04-21 21:50:36.232 D/MountService( 1269):     mAllowMassStorage=false mMaxFileSize=0 mOwner=UserHandle{0} mUuid=null 

04-21 21:50:36.232 D/MountService( 1269):     mUserLabel=null mState=null mAllowMtp=true 

04-21 21:50:36.232 D/MountService( 1269): got storage path: /storage/sdcard1 description: SD卡 primary: false removable: true emulated: false mtpReserve: 0 allowMassStorage: true maxFileSize: 0 allowMtp: true

04-21 21:50:36.232 D/MountService( 1269): addVolumeLocked() StorageVolume:

04-21 21:50:36.232 D/MountService( 1269):     mStorageId=0 mPath=/storage/sdcard1 mDescriptionId=17040810 mPrimary=false 

04-21 21:50:36.232 D/MountService( 1269):     mRemovable=true mEmulated=false mMtpReserveSpace=0 mAllowMassStorage=true 

04-21 21:50:36.232 D/MountService( 1269):     mMaxFileSize=0 mOwner=null mUuid=null mUserLabel=null mState=null 

04-21 21:50:36.232 D/MountService( 1269):     mAllowMtp=true 

04-21 21:50:36.232 D/MountService( 1269): got storage path: /storage/uicc0 description: 电话卡存储设备 primary: false removable: true emulated: false mtpReserve: 0 allowMassStorage: true maxFileSize: 0 allowMtp: true

04-21 21:50:36.232 D/MountService( 1269): addVolumeLocked() StorageVolume:

04-21 21:50:36.232 D/MountService( 1269):     mStorageId=0 mPath=/storage/uicc0 mDescriptionId=17040812 mPrimary=false 

04-21 21:50:36.232 D/MountService( 1269):     mRemovable=true mEmulated=false mMtpReserveSpace=0 mAllowMassStorage=true 

04-21 21:50:36.232 D/MountService( 1269):     mMaxFileSize=0 mOwner=null mUuid=null mUserLabel=null mState=null 

04-21 21:50:36.232 D/MountService( 1269):     mAllowMtp=true 

04-21 21:50:36.232 D/MountService( 1269): got storage path: /storage/uicc1 description: 电话卡存储设备 primary: false removable: true emulated: false mtpReserve: 0 allowMassStorage: false maxFileSize: 0 allowMtp: false

04-21 21:50:36.233 D/MountService( 1269): addVolumeLocked() StorageVolume:

04-21 21:50:36.233 D/MountService( 1269):     mStorageId=0 mPath=/storage/uicc1 mDescriptionId=17040812 mPrimary=false 

04-21 21:50:36.233 D/MountService( 1269):     mRemovable=true mEmulated=false mMtpReserveSpace=0 mAllowMassStorage=false 

04-21 21:50:36.233 D/MountService( 1269):     mMaxFileSize=0 mOwner=null mUuid=null mUserLabel=null mState=null 

04-21 21:50:36.233 D/MountService( 1269):     mAllowMtp=false 

04-21 21:50:36.233 D/MountService( 1269): got storage path: /storage/usbotg description: USB存储器 primary: false removable: true emulated: false mtpReserve: 0 allowMassStorage: false maxFileSize: 0 allowMtp: true

04-21 21:50:36.233 D/MountService( 1269): addVolumeLocked() StorageVolume:

04-21 21:50:36.233 D/MountService( 1269):     mStorageId=0 mPath=/storage/usbotg mDescriptionId=17040811 mPrimary=false 

04-21 21:50:36.233 D/MountService( 1269):     mRemovable=true mEmulated=false mMtpReserveSpace=0 mAllowMassStorage=false 

04-21 21:50:36.233 D/MountService( 1269):     mMaxFileSize=0 mOwner=null mUuid=null mUserLabel=null mState=null 

04-21 21:50:36.233 D/MountService( 1269):     mAllowMtp=true